U.S. patent number 9,201,308 [Application Number 13/936,656] was granted by the patent office on 2015-12-01 for water-rich stripping and cleaning formulation and method for using same.
This patent grant is currently assigned to Air Products and Chemicals, Inc.. The grantee listed for this patent is AIR PRODUCTS AND CHEMICALS, INC.. Invention is credited to Gautam Banerjee, Yi-Chia Lee, Wen Dar Liu, Madhukar Bhaskara Rao, Thomas Michael Wieder, Aiping Wu.
United States Patent |
9,201,308 |
Rao , et al. |
December 1, 2015 |
Water-rich stripping and cleaning formulation and method for using
same
Abstract
The present invention relates to water-rich formulations and the
method using same, to remove bulk photoresists, post-etched and
post-ashed residues, residues from Al back-end-of-the-line
interconnect structures, as well as contaminations. The formulation
comprises: hydroxylamine; corrosion inhibitor containing a mixture
of alkyl dihydroxybenzene and hydroxyquinoline; an alkanolamine, a
water-soluble solvent or the combination of the two; and at least
50% by weight of water.
Inventors: |
Rao; Madhukar Bhaskara
(Fogelsville, PA), Banerjee; Gautam (Latham, NY), Wieder;
Thomas Michael (Emmaus, PA), Lee; Yi-Chia (Danshuei Jen
Taipei, TW), Liu; Wen Dar (Chupei, TW), Wu;
Aiping (Macungie, PA) |
Applicant: |
Name |
City |
State |
Country |
Type |
AIR PRODUCTS AND CHEMICALS, INC. |
Allentown |
PA |
US |
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Assignee: |
Air Products and Chemicals,
Inc. (Allentown, PA)
|
Family
ID: |
43066059 |
Appl.
No.: |
13/936,656 |
Filed: |
July 8, 2013 |
Prior Publication Data
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Document
Identifier |
Publication Date |
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US 20130296215 A1 |
Nov 7, 2013 |
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Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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12859624 |
Aug 19, 2010 |
8518865 |
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61238268 |
Aug 31, 2009 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
C11D
7/06 (20130101); G03F 7/426 (20130101); C11D
3/0073 (20130101); C11D 11/0047 (20130101); C11D
7/5004 (20130101); C11D 7/3218 (20130101); G03F
7/425 (20130101); C11D 7/3281 (20130101); C11D
7/261 (20130101); C23G 1/22 (20130101) |
Current International
Class: |
G03F
7/42 (20060101); C11D 3/00 (20060101); C11D
11/00 (20060101); C11D 7/32 (20060101); C11D
7/26 (20060101); C11D 7/06 (20060101); C11D
7/50 (20060101) |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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1875325 |
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11-119444 |
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11-194505 |
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2000056480 |
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2000-199971 |
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JP |
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2001500922 |
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JP |
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2007526523 |
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JP |
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JP |
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9836045 |
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Aug 1998 |
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WO |
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9960083 |
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WO |
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Sep 2005 |
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WO |
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2006112994 |
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Oct 2006 |
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WO |
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Primary Examiner: Webb; Gregory
Attorney, Agent or Firm: Yang; Lina
Claims
The invention claimed is:
1. A water-rich stripping and cleaning formulation, consisting
essentially of: from 1 to 30% by weight of at least one selected
from a hydroxylamine, a hydroxylamine salt compound, and mixtures
thereof; from 0.1 to 5% by weight of a corrosion inhibitor
containing a mixture of alkyl dihydroxybenzene and
hydroxyquinoline; one component selected from the group consisting
of from 5% to 45% by weight of an alkanolamine which is miscible
with said hydroxylamine, from 5% to 45% by weight of a
water-soluble solvent, and combinations thereof; and at least 50%
by weight of water.
2. The formulation as claimed in claim 1, wherein the alkyl
dihydroxybenzene has linear or branched alkyl group containing 2-6
carbon atoms, and the hydroxyquinoline is selected from group
consisting of 2-hydroxyquinoline, 4-hydroxyquinoline,
6-hydroxyquinoline, and 8-hydroxyquinoline.
3. The formulation as claimed in claim 1, wherein the alkyl
dihydroxybenzene is tertiary butyl catechol, and the
hydroxyquinoline is 8 hydroxyquinoline.
4. The formulation as claimed in claim 1, wherein the one component
is the alkanolamine selected from the group consisting of
monoethanolamine, aminoethoxyethanol, aminopropylmorpholine,
monoethanolamine, N-methyl ethanolamine, N-ethyl ethanolamine,
N,N-dimethylethanolamine, N,N-diethyl ethanolamine, N-methyl
diethanolamine, N-ethyl diethanolamine, diethanolamine, triethanol
amine, tertiarybutyldiethanol amine, isopropanolamine,
2-amino-1-propanol, 3-amino-1-propanol, 2-amino-1-butanol,
isobutanolamine, 2-amino-2-ethoxypropanol, 2-amino-2-ethoxyethanol,
and mixtures thereof.
5. The formulation as claimed in claim 4, wherein the alkyl
dihydroxybenzene is tertiary butyl catechol, the hydroxyquinoline
is 8-hydroxyquinoline, and the alkanolamine is
monoethanolamine.
6. The formulation as claimed in claim 1, wherein the one component
is the water-soluble solvent selected from the group consisting of
ethylene glycol, propylene glycol, benzyl alcohol, dimethyl
sulfoxide, dimethylurea, glycerol, dipropylene glycol monomethyl
ether, n-methyl pyrrolidone, tetrahydrofurfural alcohol,
tetramethoxyethane, and mixtures thereof.
7. The formulation as claimed in claim 6, wherein the alkyl
dihydroxybenzene is tertiary butyl catechol, the hydroxyquinoline
is 8-hydroxyquinoline, and the water-soluble solvent is selected
from the group consisting of ethylene glycol, propylene glycol,
benzyl alcohol, dimethyl sulfoxide, dimethylurea, glycerol,
dipropylene glycol monomethyl ether, n-methyl pyrrolidone,
tetrahydrofurfural alcohol, tetramethoxyethane, and mixtures
thereof.
8. The formulation as claimed in claim 1, wherein the one component
is the combination of the alkanolamine miscible with said
hydroxylamine and the water-soluble solvent.
9. The formulation as claimed in claim 8, wherein the alkanolamine
is monoethanolamine, and the water-soluble solvent is selected from
the group consisting of ethylene glycol, propylene glycol, benzyl
alcohol, dimethyl sulfoxide, dimethylurea, glycerol, dipropylene
glycol monomethyl ether, n-methyl pyrrolidone, tetrahydrofurfural
alcohol, tetramethoxyethane, and mixtures thereof.
10. The formulation as claimed in claim 1, wherein the alkyl
dihydroxybenzene is tertiary butyl catechol, the hydroxyquinoline
is 8-hydroxyquinoline, the alkanolamine is monoethanolamine, and
the water-soluble solvent is selected from the group consisting of
ethylene glycol, propylene glycol, benzyl alcohol, dimethyl
sulfoxide, dimethylurea, glycerol, dipropylene glycol monomethyl
ether, n-methyl pyrrolidone, tetrahydrofurfural alcohol,
tetramethoxyethane, and mixtures thereof.
11. A method of removing photoresist, etch or ash residue, and
contaminants from a semiconductor substrate, comprising: contacting
the semiconductor substrate with a formulation comprising: from 1
to 30% by weight of at least one selected from a hydroxylamine, a
hydroxylamine salt compound, and mixtures thereof; from 0.1 to 5%
by weight of a corrosion inhibitor containing a mixture of alkyl
dihydroxybenzene and hydroxyquinoline; one component selected from
the group consisting of from 5% to 45% by weight of an alkanolamine
which is miscible with said hydroxylamine, from 5% to 45% by weight
of a water-soluble solvent, and the combinations thereof; and at
least 50% by weight of water.
12. The method as claimed in claim 11, wherein the alkyl
dihydroxybenzene has linear or branched alkyl group contains 2-6
carbon atoms, and the hydroxyquinoline is selected from group
consisting of 2-hydroxyquinoline, 4-hydroxyquinoline,
6-hydroxyquinoline, and 8 hydroxyquinoline.
13. The method as claimed in claim 11, wherein the alkyl
dihydroxybenzene is tertiary butyl catechol, and the
hydroxyquinoline is 8 hydroxyquinoline.
14. The method as claimed in claim 11, wherein the one component is
the alkanolamine selected from the group consisting of
monoethanolamine, aminoethoxyethanol, aminopropylmorpholine,
monoethanolamine, N-methyl ethanolamine, N-ethyl ethanolamine,
N,N-dimethylethanolamine, N,N-diethyl ethanolamine, N-methyl
diethanolamine, N-ethyl diethanolamine, diethanolamine, triethanol
amine, tertiarybutyldiethanol amine, isopropanolamine,
2-amino-1-propanol, 3-amino-1-propanol, 2-amino-1-butanol,
isobutanolamine, 2-amino-2-ethoxypropanol, 2-amino-2-ethoxyethanol,
and mixtures thereof.
15. The method as claimed in claim 14, wherein the alkyl
dihydroxybenzene is tertiary butyl catechol, the hydroxyquinoline
is 8-hydroxyquinoline, and the alkanolamine is
monoethanolamine.
16. The method as claimed in claim 11, wherein the one component is
the water-soluble solvent selected from the group consisting of
ethylene glycol, propylene glycol, benzyl alcohol, dimethyl
sulfoxide, dimethylurea, glycerol, dipropylene glycol monomethyl
ether, n-methyl pyrrolidone, tetrahydrofurfural alcohol,
tetramethoxyethane, and mixtures thereof.
17. The method as claimed in claim 16, wherein the alkyl
dihydroxybenzene is tertiary butyl catechol, the hydroxyquinoline
is 8-hydroxyquinoline, and the water-soluble solvent is selected
from the group consisting of ethylene glycol, propylene glycol,
benzyl alcohol, dimethyl sulfoxide, dimethylurea, glycerol,
dipropylene glycol monomethyl ether, n-methyl pyrrolidone,
tetrahydrofurfural alcohol, tetramethoxyethane, and mixtures
thereof.
18. The method as claimed in claim 11, wherein the one component is
the combination of the alkanolamine miscible with said
hydroxylamine and the water-soluble solvent.
19. The method as claimed in claim 18, wherein the alkanolamine is
monoethanolamine, and the water-soluble solvent is selected from
the group consisting of ethylene glycol, propylene glycol, benzyl
alcohol, dimethyl sulfoxide, dimethylurea, glycerol, dipropylene
glycol monomethyl ether, n-methyl pyrrolidone, tetrahydrofurfural
alcohol, tetramethoxyethane, and mixtures thereof.
20. The method as claimed in claim 11, wherein the alkyl
dihydroxybenzene is tertiary butyl catechol, the hydroxyquinoline
is 8-hydroxyquinoline, the alkanolamine is monoethanolamine, and
the water-soluble solvent is selected from the group consisting of
ethylene glycol, propylene glycol, benzyl alcohol, dimethyl
sulfoxide, dimethylurea, glycerol, dipropylene glycol monomethyl
ether, n-methyl pyrrolidone, tetrahydrofurfural alcohol,
tetramethoxyethane, and mixtures thereof.
Description
BACKGROUND OF THE INVENTION
Conventional stripping and cleaning formulations for Al back-end-of
the-line (Al BEOL) cleaning of ashed and unashed substrates
typically contain a hydroxlyamine, a solvent (optional), an
alkanolamine (optional), water and a corrosion inhibitor or
chelating agent. Conventional chemistries typically contain a
majority of organic components and amines and a minority of water.
Typical examples of such chemistries are seen in U.S. Pat. No.
5,911,835, U.S. Pat. No. 6,110,881, U.S. Pat. No. 6,319,885, U.S.
Pat. No. 7,051,742, and U.S. Pat. No. 7,144,849. In the above
listed patents, dihydroxy-aromatic corrosion inhibitors, of which
catechol (dihydroxybenzene) is commonly used. Catechol has been
used as a corrosion inhibitor for aluminum. In addition, catechol
has been used as a chelating agent to extend the stability of
hydroxylamine-containing formulation.
It is well known to those in the art that a key property of an
effective cleaner is its ability to attack and/or dissolve
post-etch and/or post-ash residues without substantially attacking
the underlying interconnect dielectric or metals, that is, the
selection of corrosion inhibitor is the key to controlling the
metal etch rate.
In BEOL applications for Al interconnect structures, the corrosion
inhibitor must be able to inhibit etching of aluminum and other
interconnect metals/film, however since aluminum is
electrochemically very active, it is most susceptible to corrosion
and/or etching.
It would therefore be desirable to provide a cleaning formulation
and process capable of removing those unwanted residues without
corroding, dissolving or dulling the exposed surfaces of the
interconnect structures. Hydroxylamine is very effective at
removing residues and unashed photoresist from semiconductor
substrates, but is susceptible to decomposition, even at room
temperature. It is critical to find components for the cleaning
formulation containing hydroxylamine that can stabilize
hydroxylamine or do not accelerate hydroxylamine decomposition.
Therefore, it would be desirable to control aluminum etch rate and
to stabilize hydroxylamine for the cleaning formulation containing
hydroxylamine.
BRIEF SUMMARY OF THE INVENTION
Accordingly, one aspect of the present invention is water-rich
formulations for removing the photoresist, post-etched and
post-ashed residues, residues from Al back-end-of-the-line
interconnect structures, as well as contaminants.
In one embodiment, the invention provides a water-rich formulation
comprising: hydroxylamine, hydroxylamine salt compound, and
mixtures thereof; alkyl-dihydroxybenzene; hydroxyquinoline; an
alkanolamine which is miscible with said hydroxylamine; and water;
wherein the water-rich formulation having at least 50% by weight of
water.
In another embodiment, the invention provides a water-rich
formulation comprising: hydroxylamine, hydroxylamine salt compound,
and mixtures thereof; alkyl-dihydroxybenzene; hydroxyquinoline; a
water-soluble solvent; and water; wherein the water-rich
formulation having at least 50% by weight of water.
Yet, in another embodiment, the invention provides a water-rich
formulation comprising: hydroxylamine, hydroxylamine salt compound,
and mixtures thereof; alkyl-dihydroxybenzene; hydroxyquinoline; an
alkanolamine which is miscible with said hydroxylamine a
water-soluble solvent; and water; wherein the water-rich
formulation having at least 50% by weight of water.
According to another aspect of the present invention, provided are
methods of removing post-etched and post-ashed residues from a
substrate comprising: applying a formulation as recited above to a
substrate to remove the photoresist, post-etched and post-ashed
residues, as well as contaminants from the substrate.
BRIEF DESCRIPTION OF SEVERAL VIEWS OF THE DRAWINGS
FIG. 1. Tafel analysis shows the plotted corrosion potential of an
electrode relative to a reference against the logarithm of the
corrosion current density.
FIG. 2. Tafel analysis of a water-rich and a solvent-rich
formulations both having catechol as the corrosion inhibitor.
FIG. 3. Stability of hydroxylamine as a function of temperature in
water-rich formulation having catechol as the corrosion
inhibitor.
FIG. 4. Stability of hydroxylamine as a function of temperature in
water-rich formulation not having catechol as the corrosion
inhibitor.
FIG. 5. Tafel analysis of water-rich formulations having (a)
tertiary butyl catechol (tBC) and 8 hydroxyquinoline (8HQ); and (b)
8 hydroxyquinoline (8HQ).
FIG. 6. Tafel analysis of water-rich formulations having (a)
tertiary butyl catechol (tBC) and 8 hydroxyquinoline (8HQ); and (b)
tertiary butyl catechol (tBC).
FIG. 7. Stability of hydroxylamine as a function of temperature in
a water-rich formulation having tertiary butyl catechol (tBC) and 8
hydroxyquinoline (8HQ).
DETAILED DESCRIPTION OF THE INVENTION
Cleaning formulations are needed for Al BEOL (back-end-of the-line)
cleaning of ashed and unashed substrates. It is well known to those
in the art that a key property of an effective cleaner is its
ability to attack and dissolve post-etch and post-ash residues
without substantially attacking the underlying interconnect
dielectric or metals; the selection of corrosion inhibitor is the
key to controlling the metal etch rate.
Aluminum is electrochemically very active, it is most susceptible
to corrosion and/or etching. For Al interconnect structures, the
corrosion inhibitor must be able to inhibit etching of aluminum and
other interconnect metals and/or films.
Conventional cleaning formulations typically contain a
hydroxlyamine, a solvent (optional), an alkanolamine (optional),
water and a corrosion inhibitor or chelating agent. One way of
modulating the corrosive effect of hydroxylamines (and amines) in
cleaning formulations is by keeping the water level low and using a
high concentration of solvent, thus solvent-rich formulations. In
many of the above listed patents, catechol has been used as a
corrosion inhibitor for aluminum and/or chelating agent to extend
the stability of hydroxylamine-containing solvent-rich
formulation.
Water-rich formulations containing hydroxylamine for Al BEOL
cleaning have been developed in the present invention. Here,
"water-rich" refers to the formulation having at least 50% by
weight of water.
The water-rich formulations typically comprise from 1 to 30% by
weight of at least one selected from a hydroxylamine, a
hydroxylamine salt compound, and mixtures thereof; from 0.1 to 5%
by weight of a corrosion inhibitor; one component selected from the
group consisting of from 5% to 45% by weight of a water-soluble
solvent, from 5% to 45% by weight of an alkanolamine which is
miscible with said hydroxylamine, and the combination of the
two.
The water-soluble solvent includes but not limited to ethylene
glycol, propylene glycol, benzyl alcohol, dimethyl sulfoxide,
dimethylurea, glycerol, dipropylene glycol monomethyl ether,
n-methyl pyrrolidone, tetrahydrofurfural alcohol,
tetramethoxyethane, and mixtures thereof.
The alkanolamine which is miscible with said hydroxylamine includes
but not limited to monoethanolamine, aminoethoxyethanol,
aminopropylmorpholine, monoethanolamine, N-methyl ethanolamine,
N-ethyl ethanolamine, N,N-dimethylethanolamine, N,N-diethyl
ethanolamine, N-methyl diethanolamine, N-ethyl diethanolamine,
diethanolamine, triethanol amine, tertiarybutyldiethanol amine,
isopropanolamine, 2-amino-1-propanol, 3-amino-1-propanol,
2-amino-1-butanol, isobutanolamine, 2-amino-2-ethoxypropanol,
2-amino-2-ethoxyethanol, and mixtures thereof.
Different corrosion inhibitors have been used for water-rich
formulations in the present invention. In addition of catechol, a
combination of organic compounds, specifically, alkyl
dihydroxybenzenes and hydroquinolines has been tested. Alkyl
dihydroxybenzenes include but not limited to those having linear or
branched alkyl group contains 2-6 carbon atoms, such as, tertiary
butyl catechol. Hydroquinolines include but not limited to
2-hydroxyquinoline, 4-hydroxyquinoline, 6-hydroxyquinoline and
8-hydroxyquinoline.
In the following working examples, catechol has been tested in
Examples 1 to 3, and a combination of tertiary butyl catechol and
8-hydroxyquinoline has been tested in Examples 4 to 5.
EXAMPLES
The following examples are provided for the purpose of further
illustrating the present invention but are by no means intended to
limit the same.
Example 1
Catechol as Corrosion Inhibitor/Chelating Agent
Three formulations with differing levels of water, solvent, and
hydroxylamine have been tested in this example. Catechol was used
as the corrosion inhibitor. Catechol was selected for the
experiments since it is a well-know corrosion inhibitor in the
field and was a common component in the patents listed above.
Table 1 listed the aluminum etch rate of three formulations.
TABLE-US-00001 TABLE 1 Aluminum etch rate for hydroxylamine
formulations with catechol as the corrosion inhibitor Formulation
Formulation A B 18647-76I Monoethanol amine 59.20 65.00 20.00
hydroxylamine 18.05 10 7.5 Catechol 4.70 5.00 5.00 Water 18.05 20
67.5 Al etch rate (ER), .ANG./min 1 1 7 Temperature .degree. C. of
ER, 55 45 45
Formulations A and B in Table 1 were lower in water (<20%), but
higher in monoethanol amine solvent (>50%). Thus, formulations A
and B were solvent-rich formulations. On the contrary, formulation
18647-761 contained higher level (>50%) water and lower level of
monoethanol amine solvent (20% or less). Therefore, formulation
18647-761 was a water-rich formulation.
As shown in Table 1, formulations A and B had lower aluminum etch
rates when catechol used as a corrosion inhibitor. Formulation
18647-761 had higher aluminum etch rates (seven times higher than
formulations A and B) when catechol was used as a corrosion
inhibitor. Clearly, the effectiveness of catechol as a corrosion
inhibitor was favored when the water level was low (.about.20% or
less). As the water level increased the aluminum etch rate has
increased substantially.
Example 2
Electrochemical Characterization of Corrosion Rate Using
Catechol
The characterization of corrosion rate was done by using Tafel
analysis method well known in electrochemistry. FIG. 1 showed a
typical plotted potential of an electrode relative to a reference
against the logarithm of the corrosion current density.
The electrochemical potential versus current density for Al/0.5 wt
% Cu samples was measured in a series of water-rich, hydroxylamine
cleaning formulations to characterize the corrosion inhibition of a
variety of inhibitors.
Tafel plots of formulations using catechol as the corrosion
inhibitor were shown in FIG. 2. Both formulation A (a solvent-rich
formulation) and formulation 18647-76I (a water-rich formulation)
were shown in FIG. 2 for comparison.
Formulation A had a lower corrosion current than formulation
18647-76I, indicating catechol as the corrosion inhibitor
functioned better in formulation A. Again, catechol was shown to be
a poor corrosion inhibitor in water-rich systems. This was
consistent with the higher Al etch rate data shown in Table 1.
Example 3
Hydroxylamine Stability in Water-Rich Formulations Using
Catechol
Catechol and other dihydroxybenzenes have been used as chelating
agents in several US patents specifically to control the stability
of the cleaning formulation (see U.S. Pat. No. 5,911,835, U.S. Pat.
No. 6,110,881, U.S. Pat. No. 6,319,885, U.S. Pat. No. 7,051,742,
and U.S. Pat. No. 7,144,849). The primary role of the chelator is
to stabilize the hydroxylamine in solution and prevent its
degradation.
The measurements of hydroxylamine stability (or the decomposition
of hydroxylamine) in water-rich formulation 18647-76I having
catechol as chelating agent were carried out. More specifically,
the normalize hydroxylamine concentration in solution in
formulation 18647-76I as a function of time was measured for sample
at room temperature, 40.degree. C., 50.degree. C., and 60.degree.
C. The results were shown in FIG. 3.
The results indicated that the amount of hydroxylamine remaining in
solution decreased dramatically as the sample temperature was
increased. In fact when the formulation was held at 60.degree. C.,
97% of the hydroxylamine was lost in one week.
Formulation 18647-78E, which contained the same level of
monoethanol amine and hydroxylamine as 18647-76I, but contained no
catechol, was tested under the same conditions. More specifically,
formulation 18647-78E, contained 20 wt % monoethanol amine, 7.5 wt
% hydroxylamine and 72.5 wt % of water.
The results were shown in FIG. 4. FIG. 4 indicated no degradation
of hydroxylamine in formulation 18647-78E, even for samples
maintained at elevated temperature. The water-rich formulations
were more stable without the "stabilizer": catechol. Based on these
data, it would be reasonable to conclude that catechol is a
catalyst to hydroxylamine decomposition in water-rich formulations
rather than a stabilizer.
Note, the results were in direct contrast to the disclosures in the
prior art. Our results indicated that the use of catechol in
water-rich formulations was not effective at stabilizing the
hydroxylamine and, in fact, the use of catechol was effective
catalyzing the decomposition or degradation of hydroxylamine.
Example 4
Effective Corrosion Inhibitors for Al Etching that do not Catalyze
Hydroxylamine Decomposition
Water-rich formulations 18647-76K, 18647-79A and 18647-78F were
tested in this example. The alkanol amine and hydroxylamine
concentrations in the formulations were held in similar levels (see
Table 2). As for the corrosion inhibitor, formulation 18647-76K
contained 1 wt % of tertiary butyl catechol (tBC) and 1 wt % of 8
hydroxyquinoline (8HQ), 18647-79A contained 1 wt % of 8
hydroxyquinoline (8HQ), and formulation 18647-78F contained 1 wt %
of tertiary butyl catechol (tBC).
TABLE-US-00002 TABLE 2 Al/0.5 Cu corrosion current for water-rich
hydroxylamine formulations from Tafel plots 18647-76K 18647-79A
18647-78F 18647-76I Monoethanol amine 20 20 20 20 hydroxylamine 7.5
7.5 7.5 7.5 Water 70.5 71.5 71.5 67.5 8-hydroxyquinoline 1 1 0 0
t-butyl catechol 1 0 1 0 catechol 5.0 Corrosion current 8 .times.
10.sup.-8 3 .times. 10.sup.-5 2 .times. 10.sup.-7 1 .times.
10.sup.-6 density i.sub.corr, A/cm.sup.2
Tafel results on two formulations 18647-76K, 18647-79A were shown
in FIG. 5. Anodic polarization curve for 18647-79A showed strong
indication for passivity, trying to achieve limiting current, while
for 18647-76K, anodic polarization curve indicated perfect active
polarization. This indicated that a passive film would likely form
on Al surface for 18647-79A, while the possibility would be absent
for 18647-76K. In terms of cleaning, this implied that there would
not be an extra effort required to remove a passive film formed on
Al by formulation 18647-76K, whereas for 18647-79A a passive film
would likely be formed which would require further effort to
remove. It is important not to leave a passiviating film on the
metal film because such films can affect the electrical performance
of the semiconductor device.
Tafel results on two formulations 18647-76K and 18647-78F were
shown in FIG. 6. Anodic polarization curve for 18647-78F showed
strong indication for passivity, trying to achieve limiting current
at a higher potential. Again, indicated that a passivating film
could be forming on the Al surface for 18647-78F, and which would
be difficult to remove.
As shown in Table 2, the corrosion currents of formulation
18647-79A 18647-78F were both higher than formulation 18647-76K,
with formulation 18647-79A approximately 2.5 orders of magnitude
higher. The corrosion current of formulation 18647-76I from FIG. 2
in Example 2 was also listed in Table 2 for comparison.
Data in FIGS. 5 and 6, and Table 2 showed a surprising result that
the combination of t-BC and 8HQ gave better corrosion inhibition of
Al corrosion than either component individually. Furthermore, the
Tafel curves for the mixed corrosion inhibitor did not show a
limiting corrosion current, indicating perfect passivation within
the range of potential evaluated. This showed the synergistic
effect of the combination of corrosion inhibitors in 18647-76K.
Al etch rates of formulation 18657-76B containing 1 wt % of
catechol, and 1 wt % of 8 hydroxyquinoline (8HQ), and formulation
18647-76K containing 1 wt % of tertiary butyl catechol (tBC) and 1
wt % of 8 hydroxyquinoline (8HQ), were measured and shown in Table
3. The alkanol amine and hydroxylamine concentrations in the
formulations were held in the same level.
The results in Table 3 showed that the etch rate at 45.degree. C.
for 18647-76B was much higher than for 18647-76K. This indicated
that the mixture of catechol and 8HQ was a poor corrosion inhibitor
for Al.
TABLE-US-00003 TABLE 3 Comparison of effect of catechol and tBC in
combination of 8HQ on Al etch rate Formulation 18647-76K 18647-76B
Monoethanol amine 20.0 20.0 hydroxyl amine 7.5 7.5 Catechol 0.0 1.0
8Hydroxyquinoline 1.0 1.0 t-butyl catechol 1.0 0.0 Water 70.5 70.5
Al etch rate (ER), A/min 1.0 70.0 Temperature of ER, C. 45.0
45.0
On the contrary, while the mixture of tBC and 8HQ was consistently
shown to be an excellent corrosion inhibitor for Al.
Example 5
Hydroxylamine Stability in Water-Rich Formulations Using the
Combination of Tertiary Butyl Catechol (tBC) and 8 Hydroxyquinoline
(8HQ)
Hydroxylamine stability (or the decomposition of hydroxylamine) in
water-rich formulation 18647-76K having the combination of 1 wt %
of tBC and 1 wt % of 8HQ, was measured. The results were shown in
FIG. 7.
The results showed that formulation 18647-76K had a very stable
hydroxylamine concentration over a wide range of temperatures for
over 6 weeks. Thus, the combination of tBC and 8HQ as the corrosion
inhibitor in water-rich stripper formulations, did not no degrade
hydroxylamine, most importantly did not catalyze the decomposition
of hydroxylamine.
Example 6
The galvanic couple current (GCC) is a measure of the oxidation
(etch rate) of an electrochemically active metal when electrically
connected to another metal when in contact with an electrolyte.
A series of formulations was prepared (see table 4) and tested as
electrolytes in galvanic couple current measurements.
In these tests, an Al/0.5 wt % Cu was the active electrode and was
connected to TiN and immersed in a cleaning formulation
(electrolyte). The current between the two metals was measured
using a galvanostat/potentiostat. Higher galvanic couple currents
indicates higher corrosion rate.
More specifically, a 400 ml Teflon beaker was filled with 250 ml of
a formulation. The sample was heated to 35.degree. C. on a hot
plate and magnetic stir bar was used to stir the solution. A 8
cm.times.2 cm piece of Al/0.5% Cu wafer was immersed to a depth of
4 cm into the formulation. A similar-sized piece of TiN was also
immersed into the formulation to the same depth. The wafer samples
were separated by a distance 4 cm. Al/0.5% Cu was the working
electrode, TiN was the counter and reference electrode. Since
Al/0.5% Cu was electrochemically active to TiN, the GCC indicates
the corrosion rate of aluminum. A Gamry galvanostat/potentiostat
was then connected to the 2 pieces. The GCC was measured over 900
secs.
First three sets of formulations were prepared with different
solvents.
Formulations 83A, 83B, and 83C contained propylene glycol.
Formulations 83D, 83E and 83F contained dipropylene glycol
monomethyl ether. Formulations 83G, 83H and 83I contained
tetrahydrofurfural alcohol.
A fourth set of formulations were prepared without solvent: they
were 18647-76K, 18647-78F, and 18647-79A.
Within each group, the corrosion inhibitor was varied to be a
mixture of 1 wt % tertbutyl catechol (tBC) and 1 wt % of 8
hydroxyquinoline (8HQ), only 1% tBC, or only 1 wt % 8HQ.
The results were shown in Table 4 below.
By comparing the galvanic couple current (GCC) of the first three
formulations within the groups, which corrosion inhibitors most
effectively reduced the GCC (i.e. suppressed Al corrosion) were
evaluated.
TABLE-US-00004 TABLE 4 Galvanic couple currents of formulations
containing solvent and various corrosion inhibitors. Component Wt %
Wt % Wt % Formulation Formulation Formulation 83A 83B 83C
Monoethanolamine 20.00 20.00 20.00 Hydroxylamine 7.50 7.50 7.50
Water 55.50 56.50 56.50 Propylene glycol 15.00 15.00 15.00
8-hydoxyquinoline 1.00 -- 1.00 Tertiary butyl 1.00 1.00 -- catechol
GCC, Amp/cm2 2.28 .times. 10.sup.-6 1.39 .times. 10.sup.-5 1.24
.times. 10.sup.-4 Formulation Formulation Formulation 83D 83E 83F
Monoethanolamine 20.00 20.00 20.00 Hydroxylamine 7.50 7.50 7.50
Water 55.50 56.50 56.50 8-hydoxyquinoline 1.00 -- 1.00 Tertiary
butyl 1.00 1.00 -- catechol Dipropylene glycol 15.00 15.00 15.00
monomethyl ether GCC, Amp/cm2 2.54 .times. 10.sup.-6 3.27 .times.
10.sup.-6 9.81 .times. 10.sup.-5 Formulation Formulation
Formulation 83G 83H 83I Monoethanolamine 20.00 20.00 20.00
Hydroxylamine 7.50 7.50 7.50 Water 55.50 56.50 56.50
8-hydoxyquinoline 1.00 -- 1.00 Tertiary butyl 1.00 1.00 -- catechol
Tetrahydrofurfural 15.00 15.00 15.00 alcohol GCC, Amp/cm2 4.55
.times. 10.sup.-6 5.15 .times. 10.sup.-5 1.51 .times. 10.sup.-4
18647-76K 18647-78F 18647-79A Monoethanolamine 20.00 20.00 20.00
Hydroxylamine 7.50 7.50 7.50 Water 70.50 71.50 71.50
8-hydoxyquinoline 1.00 -- 1.00 Tertiary butyl 1.00 1.00 -- catechol
GCC, Amp/cm2 1.08 .times. 10.sup.-6 2.65 .times. 10.sup.-5 1.55
.times. 10.sup.-4
Table 4 indicated that the lowest galvanic couple current was
always obtained when the mixture of 1 wt % tBC and 1 wt % 8HQ was
used. The formulations containing only 1% tBC or only 1% 8HQ had a
higher GCC indicating a higher Al corrosion rate. These data
indicated that mixture of the two inhibitors is preferred over
either one individually.
A fifth set of formulations were prepared with corrosion inhibitors
having methyl dihydroxybenzenes in combination with 8
hydroxyquinoline. Two methyl dihydroxybenzenes: 2 methyl recorsinol
(2MR) and methylhydroquinone (MHQ) were used: 4B and 4G with 2MR
shown in Table 5, and 4C and 4H with MHQ were shown in Table 6.
TABLE-US-00005 TABLE 5 Effect of 2-methylresorcinol (2MR) and 8HQ
as corrosion inhibitors Formulation 4B Formulation 4G Formulation
79A Component Wt % Wt % Wt % Monoethanolamine 20.00 20.00 20.00
Hydroxylamine 7.50 7.50 7.50 Water 70.75 71.75 71.50
8-hydoxyquinoline 1.00 0.00 1.00 2-methylresorcinol 0.75 0.75 0.00
GCC, A/cm2 1.66 .times. 10.sup.-04 7.08 .times. 10.sup.-05 1.55
.times. 10.sup.-04
The effect of formulations having methyl dihydroxybenzenes in
combination with 8 hydroxyquinoloine on GCC were shown in both
Table 5 and 6. Formulations 4B, 4G, 4C and 4H were also compared to
formulation 18647-79A.
Formulations with methyl dihydroxybenzenes [2 methyl recorsinol
(2MR) and methylhydroquinone (MHQ)] showed different GCC behavior
compared to tBC in combination with 8HQ, formulations with 2MR and
MHQ showed GCC values higher than when they were alone in the
formulation. This indicates that the methyl dihydroxybenzenes
enhance corrosion in the presence of 8HQ.
TABLE-US-00006 TABLE 6 Effect of Methyl hydroquinone (MHQ) and 8HQ
as corrosion inhibitors Formulation Formulation Formulation 4C 4H
79A Component Wt % Wt % Wt % Monoethanolamine 20.00 20.00 20.00
Hydroxylamine 7.50 7.50 7.50 Water 70.75 71.75 71.50
8-hydoxyquinoline 1.00 0.00 1.00 methyl hydroquinone 0.75 0.75 0.00
GCC, A/cm2 2.51 .times. 10.sup.-04 1.70 .times. 10.sup.-04 1.55
.times. 10.sup.-04
A seventh set of formulations were prepared with different
water-soluble solvent and no monoethanolamine: formulations 9M, 9N,
9O were prepared using dipropylene glycol monomethyl ether.
TABLE-US-00007 TABLE 7 Effect of Solvent Formulation 9N Formulation
9O Formulation 9M Component Wt % Wt % Wt % Dipropylene glycol 20.00
20.00 20.00 monomethyl ether Hydroxylamine 10.00 10.00 10.00 Water
69.30 69.50 69.80 8-hydoxyquinoline 0.20 0.00 0.20 t-Butyl catechol
0.50 0.50 0.00 GCC, A/cm2 6.06 .times. 10.sup.-08 6.08 .times.
10.sup.-06 6.67 .times. 10.sup.-08
A eighth set of formulations were prepared with different
concentration of corrosion inhibitors (see Table 8): formulations
10A, 10B and 9F. The corrosion inhibitors were the combination of
tBC and 8HQ.
The impact of the corrosion inhibitor concentration change was
shown in Table 8. Formulations 10A, 10B and 9F used tBC and 8HQ at
a total of 4%. Again, the combination of the two corrosion
inhibitors gives lower GCC than either of them used
individually.
It is understood by those in the art that the corrosion inhibitors
must be soluble in the solution to be effective. Adding corrosion
inhibitors to solutions beyond their solubility limit will not
improve corrosion inhibition and will cause other issues in
semiconductor wafer cleaning, such as deposition of solid particles
onto the wafer surface. The formulations had a upper limitation for
the total of the corrosion inhibitors not more than 5%.
TABLE-US-00008 TABLE 8 Effect of Corrosion inhibitor concentration
Formulation Formulation Formulation 10A 10B 9F Component Wt % Wt %
Wt % Monoethanolamine 20.00 20.00 20.00 Hydroxylamine 7.50 7.50
7.50 Water 68.50 70.50 70.50 8-hydoxyquinoline 2.00 0.00 2.00
T-Butyl catechol 2.00 2.00 0.00 GCC, A/cm2 1.03E .times. 10.sup.-07
1.56 .times. 10.sup.-07 2.58 .times. 10.sup.-04
The results from Examples 1 to 3 have shown that catechol was not
an effective corrosion inhibitor and was not effective at
stabilizing the hydroxylamine. In fact, the use of catechol was
effective catalyzing the decomposition or degradation of
hydroxylamine contained in the water-rich formulations.
The results from Example 4 and 5 have shown that combinations of
tBC and 8HQ were excellent corrosion inhibitors for aluminum and
excellent stabilizers for hydroxylamine contained in the water-rich
formulations. The results were compared with when catechol used
alone, either of the components: tBC or 8HQ used alone
individually, and the mixtures of catechol with either of the
components.
The results from Example 6 had several teachings.
The lowest galvanic couple current was obtained when the mixtures
of tBC and 8HQ was used comparing with either of them used
individually. This result was the same when the formulations
containing monoethanolamine without water-soluble solvents,
water-soluble solvents without monoethanolamine, or the combination
of monoethanolamine and different water-soluble solvents. Again,
the results have indicated that combinations of tBC and 8HQ were
excellent corrosion inhibitors for aluminum.
Furthermore, the methyl dihydroxybenzenes have been found to
enhance corrosion in the presence of 8HQ.
Finally, it was found the total corrosion inhibitors in the
formulation has an upper limit.
In conclusion, a water-rich formulation containing hydroxlyamine
having the mixed components of alkyl dihydroxybenzenes (such as
tertiary butyl catechol or t-BC) and a hydroxyquinoline (such as 8
hydroxyquinoline or 8HQ) has: (1) lower Al corrosion rate (as
determined from electrochemical measurements), and (2) excellent
stability of hydroxylamine in the formulation.
The foregoing examples and description of the preferred embodiments
should be taken as illustrating, rather than as limiting the
present invention as defined by the claims. As will be readily
appreciated, numerous variations and combinations of the features
set forth above can be utilized without departing from the present
invention as set forth in the claims. Such variations are not
regarded as a departure from the spirit and scope of the invention,
and all such variations are intended to be included within the
scope of the following claims.
* * * * *